A hybrid UHF narrow-band filter design

Hybrid filters composed of lumped elements and transmission-line elements are described. The basis of the filters is the split-ring resonator, a quarter-wave open line whose ends are bridged by a capacitor, which is equivalent to a shunt LC. The issues described are (1) the addition of a shunt capacitor to raise the resonator Q and (2) equivalent-circuit and design equations for the augmented split-ring resonator. Design equations are presented to implement the coupled-resonator approach to narrowband filter design. Some examples of designs and their computed responses, including losses, are presented and discussed. These filters have an advantage in board space and insertion loss over conventional coupled-line designs